


What the Mind Forgets

by Crazy_Pairing_Person



Category: Haikyuu!!
Genre: Alternate Universe, Alternate Universe - Canon Divergence, Amnesia, Angst, Childhood Friends, Crying, Eventual Fluff, Fluff, Fluff and Angst, Gen, Hanahaki Disease, Heavy Angst, Hospitals, M/M, Memory Alteration, Memory Loss, Near Death Experiences, Protective Tsukishima Kei, Surgery, Tsukishima Kei is Bad at Feelings
Language: English
Status: In-Progress
Published: 2020-06-02
Updated: 2020-07-08
Packaged: 2021-03-03 21:46:57
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 7
Words: 3,948
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24512554
Author URL: https://archiveofourown.org/users/Crazy_Pairing_Person/pseuds/Crazy_Pairing_Person
Summary: Yamaguchi never told Tsukishima about the hanahaki. Not until he collapsed on the sidewalk, coughing up more blood than flowers.Yamaguchi never intended to get the operation. Not until Tsukishima broke down in tears in the middle of the hospital, begging him to do it, to not die.And Tsukishima never thought that he was the reason Yamaguchi could have died.Not until Yamaguchi's mother asked him to not speak to his best friend in the world for an entire month.-Wherein memories are lost, as are friendships, and Tsukishima waits patiently for the day that he's allowed to be at Yamaguchi's side once more.If only Yamaguchi was less stubborn about recovering the lost pieces of his memory.
Relationships: Tsukishima Kei & Karasuno Volleyball Club, Tsukishima Kei & Yamaguchi Tadashi, Tsukishima Kei/Yamaguchi Tadashi, Yamaguchi Tadashi & Karasuno Volleyball Club
Comments: 20
Kudos: 123





	1. Prologue

**Author's Note:**

  * Translation into Français available: [What the Mind Forgets](https://archiveofourown.org/works/24591574) by [FriedCactus (CamaradeCactus)](https://archiveofourown.org/users/CamaradeCactus/pseuds/FriedCactus)



> Hanahaki disease AU that gets resolved before the character can get the operation and/or die? Boring, tired, done.
> 
> Hanahaki disease AU where everything has to be dealt with when the character has no recollection of who they once loved? New, fresh, exciting, and also good fuel for the tears I require for my monthly sacrifice to Satan.
> 
> ...What, you thought I just wrote angst for the heck of it?
> 
> Anyway, enjoy!

"Tsukki!"

Tsukishima lifted his head at the familiar voice, at the nickname he only allowed from one person in the world. "Yamaguchi," he replied as a greeting. Then, he frowned. "You look awful. Did you not sleep well?"

Yamaguchi came to a stop, giving a nervous laugh as he ducked his head. Tsukishima could see the tips of his ears turning red. "Ah... I guess not. Sorry, Tsukki. Guess I can't hide much from you, huh?"

"Of course you can't, idiot," Tsukishima muttered. He checked the clock on his phone. "C'mon. We've got time to stop by a convenience store. You need some coffee or something to wake yourself up."

"O-oh, but I don't think I have any money..." Yamaguchi muttered as he followed after Tsukishima. The blond could hear him rustling in his pockets as he spoke, and the sound drew an annoyed 'tch' from him.

"Idiot. I don't remember saying _you'd_ be buying it."

That made Yamaguchi pause for a moment, and then a hollow, fake-sounding laugh came from him. "Tsukki, it's fine, I'm fine. We've got practice, so the exercise will-"

"Make you even more exhausted. You'll be lucky to stay awake until lunch," Tsukishima said. "Besides, you always buy me stuff from the cafe. Let me do something for you in return for once. Idiot."

When Tsukishima didn't hear Yamaguchi continuing to follow him, he turned, a clear annoyed look on his eyes. "Yamaguchi, come on," he said, his tone leaving no room for argument, the words leaving his lips before he had even properly taken in his best friend's appearance.

Yamaguchi was kneeling over, bent in half, with one hand over his stomach and the other pressed to his mouth. His eyes were clenched shut, but Tsukishima could still see the tears pricking at their corners, threatening to spill.

Just like that, Tsukishima forgot about the coffee and rushed to Yamaguchi's side. "What the hell? Are you sick? Are you going to throw up? Wha-"

"Tsukki..." Yamaguchi removed his hand from his mouth just enough to speak. "Don't... You're making it..."

A loud cough wrenched its way out of his throat before he could continue. Tsukishima felt ice replace his warm blood, and he knelt down in front of Yamaguchi, trying to discern what the problem was. He placed one trembling hand at the freckled teen's shoulder. "Yamaguchi," he said, his voice shaking more than he'd normally like. "Yamaguchi, look at me. What's wrong? Why won't you look at me?"

Yamaguchi shook his head rapidly, and with one hand he shoved away Tsukishima's hand. "I'm f-fi-"

The lie, the desperate denial, wasn't even fully out of the other male's mouth before something else came surging out. Tsukishima watched with horror as Yamaguchi's legs gave out entirely underneath himself, and a horrid mixture of blood and flowers came forcing their way past the tan male's lips, plopping in big, disgusting globs onto the sidewalk.

Tsukishima didn't think twice before he'd whipped out his phone and called for his mother, begging her to come get him and Yamaguchi and take them both to the hospital. He spoke fast, desperate, and he had to repeat himself a couple of time because his voice was shaking so much.

And then, once his mother was on her way, and promising to call Yamaguchi's parents too, Tsukishima dropped to his knees, trying to catch the tearful, glazed-over eyes of his best friend - who seemed hellbent on not looking him in the eye.

"How long?" he managed to choke out. "How long have you been hiding this from me?"

Yamaguchi had no response. But Tsukishima didn't need one.

The fact that more blood had escaped his body than flower petals had was tell enough that it had been a while.

And he... Tsukishima had not noticed even a little bit. He had been so oblivious to his best friend's suffering for far too long. Had this been him, if he had the gene to get this disease, Yamaguchi likely would have noticed before he himself did. Because Yamaguchi had always been a better friend than he deserved.

Without realizing, Tsukishima had soon joined Yamaguchi in shedding tears.

Practice and school would have to wait. After all... Yamaguchi's life was far, far more important.


	2. Chapter 2

"What the hell do you mean, you're not getting the operation?"

Tsukishima's voice was filled with more venom than he would usually direct at who he was currently speaking to. But then, this person - his best friend - usually wasn't saying he intended to die, so it looked like today was the day for lots of new things.

Yamaguchi averted his eyes, arms wrapped around himself as if it would protect him from the angry glare Tsukishima was giving him. "I'm sixteen," he said defensively. "I can decline the operation if I want. My parents can't do anything about that - and you certainly can't either."

"Like hell I can't," Tsukishima spat. His fists clenched at his sides. "I'll tie you to that operating table myself if I have to. I'll reach into your mouth and yank out those flowers like I'm weeding a damn garden. One way or the other, you're getting this crap removed. I am _not_ letting you die, you fucking moron."

Yamaguchi barked out a harsh, hollow laugh. "Oh, you're not, are you?" he said, turning a venomous glare of his own over to Tsukishima. The sight was enough to make the blond falter - but glares weren't all his friend had up his sleeve. "Pretty sure it'd be illegal for you to perform that operation yourself. Hell, even most brain surgeons aren't legally allowed to perform it because of how deadly it can be. You don't want me to die, yet you're threatening to basically kill me with your own hands. Tell me, _Tsukishima_ , do you _see_ the irony in that statement, or are those glasses of yours just for show?"

Tsukishima stared at Yamaguchi, his jaw slack and eyes wide. If the words themselves had not been enough to shock him into that state, the vicious way Yamaguchi spoke his name would have been. He spoke it as though the mere existence of him was a poisonous blight on the world.

This was his best friend. The one who had always been at his side through thick and thin. They'd never so much as given each other the silent treatment, let alone had they ever been in a real fight like this.

He had never, ever seen Yamaguchi look at him like that.

And to think it was because Tsukishima wanted him to _live_... To think that it was because Yamaguchi was fine with simply _dying_...

Before he could stop himself, Tsukishima burst into tears. Because Yamaguchi was trying to take himself away. He was trying to leave Tsukishima all alone, trying to get rid of the one and only friend Tsukishima had ever truly had.

He couldn't handle the thought of a life without Yamaguchi in it.

It made him feel like the world around him would crumble and break, just at the very thought of it. He didn't want to see how he'd feel if it actually happened.

Now, Yamaguchi was the one staring with a slack jaw. Because Tsukishima never cried like this. Not in public and not when they were alone. He would sniffle and silently let tears fall, but Yamaguchi had never seen him openly sob like a child - not even when he _was_ a child.

"Tsu... Tsukki...?"

"Please, Yamaguchi," Tsukishima managed to choke out through his sobbing. "Please. You can't d-die... I don't want to l-lose you... Please... You're my only friend... My best friend... Please don't leave me alone... Please..."

Yamaguchi averted his eyes, his fingers going down to toy with the band he'd been given upon entering the hospital. A machine next to the bed he was in beeped in time with his pulse, the only sound in the room aside from Tsukishima's desperate sobbing and sniffling. "I'm not your only-"

"You are," Tsukishima insisted before the sentence could be finished. "You're the one who... Who knows me the best... You know me better than my own family... I h-have other f-friends but you're... You're different from all of the t-teammates... Y-you've always been w-with me and... I don't... I-I don't want to lo-ose you... D-don't make me lose you... I..." He let out a strangled gasp. "Please... Y-Yamaguchi, please..."

"Tsukki..." Yamaguchi sighed, and folded his hands carefully. "Okay... Okay, I'll do it. I'll get the operation."

At the words, Tsukishima let out another pathetic sniffle and he scrubbed at his eyes. "R... Really...?"

"Yeah..." Yamaguchi sighed. "I... I need to let go of these feelings anyway. And I don't want you to be... Alone. So I'll get it." He swallowed thickly. "Go... Go let them know. They said I have to sign some papers and stuff before I can do it."

"Y-yeah," Tsukishima said. "Yeah, okay. I'll go." He let out a shaky sigh. "I'll be back with them."

Yamaguchi gave Tsukishima a soft, sad-looking smile. "Okay. See you later, Tsukki."

Tsukishima left the room, meeting the eyes of his mother as well as Yamaguchi's. "He said he'll do it," he said. "He'll get the operation."

Both women sighed in relief. "Thank you for convincing him, Kei-kun," Yamaguchi's mother said with a smile. "I knew you'd be able to get through to him."

Tsukishima jerked his head in a short nod. "Yeah... Where's the doctor?"

"I'll go get him. You should get to school," Yamaguchi's mother said.

Tsukishima frowned at that. "No," he said, simple yet defiant. "My best friend needs me. I'm not going to school until I know he's going to be fine."

"He will be fine," his own mother said then. "This is a hospital, Kei, it's perfectly safe. They all know what to do to keep Tadashi-kun safe."

Tsukishima knew that, logically. He did. But something nagged at him, something in the back of his mind whispering that he needed to stay. He looked at both of the women desperately, but both looked back with similarly stern, yet comforting, expressions. "You can come see him after school today," his mother said. "But you have to go to class, at the very least so you can get homework to bring to him later. Right?"

He couldn't argue with that. His heart sank, and he nodded. "Okay... I'll go."

But even as he left the hospital, that voice whispered, nagged, begged him to stay at his best friend's side...


	3. Chapter 3

Yamaguchi had forgotten - almost - how many pictures he had of him and Tsukishima in his phone. So many... Mostly ones that he himself had insisted on taking.

They all had to go.

He looked at each and every one carefully. Examining the sparkle in his own eyes. The annoyed, yet affectionate, glint in Tsukishima's.

And then he would delete them, once he was satisfied. Once he felt that he had committed each one to a memory that would soon no longer exist.

Once every single picture that involved Tsukishima was gone - there were more than he'd honestly thought there would be at first - he moved on to the texts.

There were even more of those. They texted every night, especially if Yamaguchi had serving practice instead of walking all the way home with his friend. Most of them were dumb, nonsensical conversations. Some of them were Yamaguchi asking about English homework.

All of them had to go, too.

Once he had gotten up to a conversation that had occurred maybe last year, he realized that he wouldn't be able to read everything else before his operation. No matter how much he wanted to, he would have to bite the bullet and go ahead and delete the entire log.

So he did. With a few taps, the conversations, the late-night texts and the weird philosophical questions, as well as the encouragement to each other before games and important tests, were all gone, never to be recovered again.

Then there was only one last thing to delete.

He went into his phone contacts, and found Tsukishima's information.

He stared down at the trash icon, trying to will his thumb to tap it. To be gone with everything, to remove any and all evidence that he had ever been friends with Tsukishima.

It wasn't as if he'd remember. It wasn't as if he'd be able to regret it after everything was over and done.

And still, he stared down at it, paralyzed in fear.

Then the door opened, and he yelped, dropping his phone into his lap. His head shot up, meeting the eyes of the surgeon.

It was time, he realized, a sort of doom setting in his stomach. It was time for him to be rid of his feelings. It was time for him to remove all memory of his best friend, as well as the love he felt.

"Are you ready?" the surgeon asked in a tone that was likely meant to be soothing, but did nothing besides increase the anxiety Yamaguchi was feeling.

All he could do was nod.

Tsukishima... Tsukki didn't want him to die.

He would be mad, after it was over. After he realized that Yamaguchi had left out some vital information of who he loved. After he realized that Yamaguchi had, even without dying, left him all alone.

But at least Yamaguchi wouldn't care about it after it was over.

That thought gave him some morbid sense of peace.


	4. Chapter 4

She looked at her son. The only sound in the room was the beeping, slow and consistent, of the monitor next to his bed, tracking his heartbeat.

He blinked slowly when she didn't speak. "Mom...?"

The word broke her resolve, and she rushed into the room, shutting the door behind herself. "Tadashi, oh, baby," she said. "You're okay... I'm so glad..."

"Calm down, Mom," he said, giving her a weak smile. "It's fine. I'm fine. Just an operation. It's not like I was going to die. They know what they're doing."

His mother was not comforted by this. "I know, but, Tadashi, baby, they said it had been going on for _years_. Why didn't you tell anyone? Why didn't you get yourself treated?"

Her son frowned, pausing to consider this. "I... Don't really remember," he admitted. "I feel like... There was someone I didn't want to lose..."

"Probably the person you loved," his mother noted. "The doctors did say that you wouldn't remember them afterward..."

He nodded a little, and her heart broke a little more at how easily he accepted this. "I'm going to go get Kei-kun," she said. "He's been waiting in the lobby for-"

"Kei-kun?"

She paused. Blinked.

Stared.

Stared at the utterly confused expression on her son's face.

"Who's that?" he asked, frowning. "Do I know them?"

Her mouth opened, but no words came out.

"I..." She paused, and slowly shut her mouth. "I'm going to go get a snack from the vending machine."

Although still confused, he accepted this excuse, and nodded his understanding. "Okay."

With that, she turned and left the hospital room, making her way straight to the lobby where one Tsukishima Kei was waiting to be allowed into his best friend's room.

The permission she would make sure he never received.


	5. Chapter 5

Tsukishima's right leg shook restlessly as he stared down at his hands, folded in front of him in his lap. He'd let Yamaguchi's mother go on ahead, alone, because Yamaguchi might be his best friend, but he was her _son_. She deserved to have a moment or two alone with him, especially after such a horrifying scare.

Still, every moment that he sat in this lobby, waiting for her to get back and bring him in to see him, was pure torture. Something inside him was already panicking and he didn't even know what it was about.

Then the adult woman's legs were visible in his eyesight, and his head shot up, staring up at her with wide eyes. "Is he okay?" he asked, noticing the oddly grim expression she wore.

She sighed, seeming to take a moment to calm herself before she spoke, "He's fine. Alive. And he doesn't seem to be in pain."

And still, she looked so, so somber. It only made the anxiety within Tsukishima spike further.

"So..." He swallowed thickly, hesitating. "Can I go see him?"

Something in her eyes flashed. "No," she said, sharply. "You can't."

Tsukishima jerked back. The anxiety spread, and he felt it showing on his face now. Something whispered to him, something tried to tell him what was going on, but he shut it out. It couldn't be true.

"Why not?"

Yamaguchi's mother faltered at that, the anger that had been there so briefly now falling into sorrow. "I'm sorry, Kei-kun," she said. "But... When I went in there, when I mentioned you... He didn't remember you."

Ice flooded Tsukishima's veins, coated his skin, and froze his mind.

Around him, he could feel, _hear_ , the world beginning to crack and crumble.

"You know what that means, right?" she said, her voice sounding almost distant as she did. "You know why-"

"It's because I'm the reason he had hanahaki," he said. The words tasted like poison in his mouth, and for a moment he wished that they were. He wished he could die, right then and there. "I... I was essentially killing him, wasn't I?"

The woman didn't respond, but that was response enough. The world gained a few more cracks.

"I'm sorry, Kei-kun, but... I don't want you to be around Tadashi anymore," she said. "The doctor was telling me before I went to see him that, if I could, keep Tadashi away from the person-"

"I know," Tsukishima interrupted. "If he spends too much time around me, he'll remember me, and that might bring the disease back, too."

He saw her nod, but he felt like his mind was far away, too lost to notice it.

Why hadn't Yamaguchi ever said anything?

Wasn't it obvious that the feelings were wholeheartedly requited?

_Of course not. Of course not, with the shitty way you treat him. Of course not. Did you not see the flowers, you complete fucking moron? It was a fucking **miracle** that he didn't think you **hated** him._

He blacked out.


	6. Chapter 6

"Yamaguchi-san, may I speak to you?"

The woman looked away from her son's sleeping face to that of the doctor who had entered the room. "Yes? Is something wrong?"

"I am here to clarify a few things about your son's recovery to you," the man explained. "I assume you've already been informed, or are aware of, the danger that could come with him associating with the person he fell for?"

She pursed her lips. "Yes," she said. Her mind flashed, showing her the utterly horrified, stricken look on Tsukishima Kei's face just hours ago. "I am aware."

The doctor nodded. "Well, the danger is usually exaggerated," he said. "So that's why I'm here to clarify it."

She paused. Stared at the man before her.

"What do you mean?"

* * *

Tsukishima hugged the soft, green object to his chest, his head downcast as tears fell onto the plush toy's surface.

He had never used a toy like this for comfort. Not once in his life.

But now he held a neon green dinosaur plush close to him, as if it would be able to protect him from the nightmare he had found himself in. The nightmare where he could no longer be Yamaguchi's friend.

And then the sound of his phone ringing jolted him from his thoughts. He yanked himself away from the stuffed animal in his grasp, letting out a strangled gasp. His head shot towards his phone, eyes wide. Who could possibly be calling right now?

Hesitantly, he grabbed his phone from beside his bed with one hand, the other clutching tightly to the dinosaur. He answered, and lifted the phone to his ear. "Hello...?"

"Kei-kun..."

His breath hitched. "Ah..." Yamaguchi's mother. "Is... Is something wrong?"

"I misspoke earlier," the woman said. "It is not that you can never come see Tadashi again. It is only a for a month."

"...A month?"

"The doctor said that after a month, his mind will have entirely locked away any memories that had to do with... With you. They won't return, nor will the disease. So after a month... You can be Tadashi's friend again, if you should like."

No.

He couldn't.

Yamaguchi wouldn't remember him. It wouldn't be the same. They could be acquaintances, but Tsukishima doubted he'd ever be able to call Yamaguchi a friend ever again.

...And yet, he would still have him in his life.

It was selfish, wasn't it? To agree? He didn't deserve Yamaguchi in his life, friend or not.

"I'll... Keep that in mind."

"Kei-kun-"

"I'm sorry, ma'am. I'm afraid I have to go, now. Homework."

A brief silence.

"Of course... Goodbye, Kei-kun."

Beep.

Tsukishima let his hand drop, his phone flopping uselessly out of it. He stared blankly down at the plush in his other hand.

"...What do you think, Rex?" he asked, despite feeling rather childish for asking a toy's advice. "Should I be Yamaguchi's friend again, when the month is up?"

The toy stared back at him, its button eyes blank and unanswering.

"...Yeah. I think so, too."


	7. Chapter 7

Tsukishima stared down at the floor rather than at the teacher's eyes, waiting for the tense, heavy silence to end.

"Tsukishima-kun... Why are you quitting the team?" the older male asked, sounding genuinely hurt and confused. "The team-"

"I'm not interested in volleyball like they are," he said, his tongue stinging with the poison of lies. He liked volleyball - loved it. His reason for quitting had nothing to do with the sport. But he couldn't tell the man his true reason. "I'll only drag them down if I stay, so I'm leaving. It's as simple as that, okay, Sensei?"

Takeda sighed deeply. "This is a true disappointment. Everyone else will be sad to see you go, Tsukishima-kun..."

"I doubt it," Tsukishima muttered under his breath.

"Yamaguchi-kun definitely will... He's staying, right?"

Tsukishima felt himself tense at the mention of his former best friend. It apparently didn't go unnoticed by Takeda, as he could suddenly feel the teacher's eyes staring at him even more intently. "Tsukishima-kun... Is something wrong between you and-"

"That's none of your business," Tsukishima snapped, his voice full of anger and venom, directed at one who was so clearly not at fault. It made him feel guilty, but he didn't dare apologize for it. "I'm quitting, okay? That's that."

And then he spun on his heel, ready to leave before his next class would start-

"You know, Ukai-kun and I received word about Yamaguchi-kun's condition."

Tsukishima froze in place, one foot hanging awkwardly over the ground, mid-step. "What."

"He had a surgery, right?" Takeda said. "The doctors wouldn't tell us what kind, but... If you're wanting to quit the team, and you're acting so defensive, then-"

"With all due respect, I don't know what you're talking about. I'm just not interested in volleyball anymore, okay?" His voice wavered, though, no longer the cold, stony wall he had previously put within his tone. "Just drop it."

_Please..._

A silence fell.

Eventually, Takeda said, "Please consider coming back, Tsukishima-kun. It would mean the world to everyone else. For now, though, feel free to do as you like."

Tsukishima didn't respond, didn't even nod. He ran out of that office, rushing to the nearest open window in the hallway. He grasped the edge of that window, gasping as cool air hit his face.

...Yamaguchi would be coming back to school the next day.


End file.
